OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 1 2022 It is necessary to use materials that ensure operability at low temperatures for such equipment. These materials should meet such requirements as strength, toughness and plasticity, corrosion resistance, resistance to fracture under abrupt changes in temperature and load application rate [1–4]. In addition, the features of equipment manufacturing should be taken into account: in some cases, it is necessary to manufacture parts by casting, by pressure, besides it is important to take into account the use of welding technologies in the assembly process [4]. Most often, metastable austenitic steels of various alloying systems are used for the manufacture of low-temperature equipment. Despite suffi cient experience in the use of such materials, not enough information is collected on the behavior of such materials at low temperatures, including phasestructural transformations, the features of such transformations in different temperature zones, including when a load is applied, both static and dynamic. There is a lack of information about the effect of stress concentrators, which always appear in equipment parts at different stages of its manufacture, on changes in the physical and mechanical properties of metastable austenitic steels [1–3, 5–20]. In order to make a conclusion about the possibility of using materials at low temperatures, including cryogenic one, it is necessary to conduct studies to assess changes in the structure and complex of properties of steels during cooling, including at abrupt temperature changes, for example, in the process of fi lling containers with a liquid cryoproduct. An analysis of the structure and properties of materials after long-term operation of low-temperature equipment made it possible to conclude that the traditionally used set of studies for choosing a material is, as a rule, insuffi cient and cannot guarantee reliable operation of equipment. This is due to the fact that numerous technological heatings during long-term operation can lead to changes in the phase-structural composition. This, in turn, can be the cause of emergency situations, leading to premature destruction of low-temperature equipment, for example, tanks and pipelines [5, 21–24]. In this regard, it is important to obtain information about the change in the phase-structural state and mechanical characteristics of metastable austenitic steels traditionally used in low-temperature equipment. The collected information on the behavior of materials will make it possible to clarify the recommendations for choosing a material for low-temperature equipment, including cryogenic one, as well as its reliability during long-term operation. The purpose of the study is to evaluate the performance of industrially used metastable austenitic steels (MAS) for its possible use instead of steel 12Cr18Ni10Ti. Study objectives: – to evaluate the joint effect of low temperatures and deformations on the processes of phase-structural transformations in metastable austenitic steels of various alloying systems; – to investigate the infl uence of the manufacturing method (cast or deformed state), the presence of stress concentrators, the rate of load application and temperature changes on the properties of austenitic steels; – to give an opinion on the possibility of replacing the traditionally used steel 12Cr18Ni10Ti for the manufacture of equipment for low-temperature equipment, including cryogenic one. Research technique Traditionally used metastable austenitic steels of Cr-Ni-Mn and Cr-N-Mn alloying systems were chosen as objects of study. The chemical composition of the industrial casts of the studied steels is given in Table. The composition was determined by the X-ray spectral method. Chemical composition of steels 10Cr14NMn20, 10Cr14Mn14Ni4Ti Steel grade Chemical element, wt. % C Si Mn Ni S P Cr N Ti Cu 10Cr14NMn20 0.10 0.5 20.3 – 0.011 0.012 14.8 0.3 0.45 – 10Cr14Mn14Ni4Ti 0.10 0.7 14.9 – 0.019 0.020 14.6 – 0.23 –
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